Apparatus and method for measuring degree of cure of adhesive agent

ABSTRACT

A degree of cure measuring apparatus has: a second optical fiber for emitting light from a tip face thereof; a probe for holding adhesive agent and irradiating the adhesive agent with light while the adhesive agent is in contact with the tip face of the second optical fiber; a detector for detecting light that is reflected from an interface between the tip face of the second optical fiber and the adhesive agent and then returns to the second optical fiber; and a computer for calculating the refractive index of the adhesive agent from the rate of the light amount of the light detected by the detector to the emission light amount from the tip face of the second optical fiber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a apparatus and a method for measuringthe degree of cure of adhesive agent.

2. Description of the Related Art

Adhesive agent such as epoxy type adhesive agent has been used in anassembling process of optical device or electronic device. It isnecessary to measure the degree of cure of adhesive agent in aproduction process using such adhesive agent for the purpose of (1)grasping the temperature and time at which adhesive agent cures anddetermining a cure condition; (2) checking whether adhesive agent iscured as expected under a specified temperature and time condition whenadhesive production lot is changed; and (3) checking whether adhesiveagent is cured as expected under a specified temperature and timecondition when the adhesive agent has been stocked for a long term.

(1) An FT-IR method (see JP-A-2007-248431, for example), (2) a DSCmethod (see JP-A-2-229741, for example) and (3) a method of measuringthe degree of cure with a micro-hardness tester (see JP-A-3-105233) andthe like are known as a method of measuring the degree of cure ofadhesive agent.

-   [Patent Document 1] JP-A-2007-248431-   [Patent Document 2] JP-A-2-229741-   [Patent Document 3] JP-A-3-105233

With respect to the FT-IR method, it is necessary to prepare manysamples under different temperature and time conditions and measure allof these samples. Therefore, much time and efforts are necessary, andalso an available measuring apparatus is expensive. With respect to theDSC method, much time is taken to prepare and measure samples, and alsoit is impossible to grasp the relationship between temperature andcuring time. With respect to the method with the micro-hardness tester,it is necessary to prepare many samples cured under differenttemperature and time conditions and also measure all of these samples;therefore, much time and efforts are necessary. In addition, this methodhas a problem that it is difficult to quantify a measurement result.

SUMMARY OF THE INVENTION

The present invention has been made in view of such circumstances, andan object of the present invention is to provide a apparatus and amethod that can measure the degree of cure of adhesive agent.

In order to solve the problem, according to an aspect of the presentinvention, there is provided a degree of cure measuring apparatus formeasuring a degree of cure of adhesive agent, including an optical fiberfor emitting light from a tip face thereof, a probe for holding theadhesive agent therein and emitting light to the adhesive agent whilethe adhesive agent is in contact with the tip face of the optical fiber,a detector for detecting light returning from an interface between thetip face of the optical fiber and the adhesive agent to the opticalfiber, and a refractive index calculator for calculating a refractiveindex of the adhesive agent from a rate of a light amount detected bythe detector to an emission light amount from the tip face of theoptical fiber.

The optical fiber may be a single mode optical fiber.

The probe may have a capillary provided to a tip portion of the opticalfiber and a cylindrical member in which the capillary is inserted, andan inner wall surface of the cylindrical member, a tip face of thecapillary and the tip face of the optical fiber may form an adhesiveagent holding space for holding the adhesive agent.

The probe further may have an enclosing member for enclosing theadhesive agent in the adhesive agent holding space, a surface of theenclosing member that faces the tip face of the optical fiber beingtilted at a predetermined angle with respect to the tip face of theoptical fiber.

The probe further may have a capillary provided to a tip portion of theoptical fiber, the capillary having a recess portion for holding theadhesive agent that is formed at a tip portion thereof.

A degree of cure measuring apparatus may have a recorder for recordingtime-variation of the refractive index calculated by the refractiveindex calculator.

Another aspect of the present invention, there is provided a degree ofcure measuring method for measuring a degree of cure of adhesive agent,including emitting light from a tip face of an optical fiber, bringingthe tip face of the optical fiber into contact with the adhesive agent,detecting light returning from an interface between the tip face of theoptical fiber and the adhesive agent to the optical fiber, andcomprising calculating a refractive index of the adhesive agent from arate of a detected light amount to an emission light amount from the tipface of the optical fiber.

According to further another aspect of the present invention, there isprovided a degree of cure measuring apparatus for measuring a degree ofcure of adhesive agent, including an optical fiber for emitting lightfrom a tip face thereof, a light guide member detachably connected tothe optical fiber and for irradiating the adhesive agent with lightwhile a light emission face thereof is in contact with the adhesiveagent, and a detector for detecting light returning from an interfacebetween the light emission face of the light guide member and theadhesive agent to the light guide member.

The light guide member may have an optical fiber piece connected to thetip face of the optical fiber.

The light guide member may have a lens that is configured to emit lightincident from the optical fiber as parallel light.

The light guide member may have a lens that is configured so that lightincident from the optical fiber is focused onto a light emission facethereof.

The light guide member may have a light guide part for irradiating theadhesive agent with light incident thereto while a light emission facethereof is in contact with the adhesive agent, and that is formed of amaterial having substantially the same refractive index as the adhesiveagent before cure.

The light guide member further may have a lens provided between theoptical fiber and the light guide part.

The degree of cure measuring apparatus may include a refractive indexcalculator for calculating a refractive index of the adhesive agent froma rate of a light amount detected by the detector to an emission lightamount from the light guide member.

The degree of cure measuring apparatus may include a recorder forrecording time-variation of the refractive index calculated by therefractive index calculator. Furthermore the degree of cure measuringapparatus may include a computer comprising a refractive indexcalculator and a recorder for recording time-change of the refractiveindex.

The optical fiber may be a single mode optical fiber.

The light guide member may have an adhesive agent holder for holding theadhesive agent.

According to further another aspect of the present invention, there isprovided a degree of cure measuring method for measuring a degree ofcure of adhesive agent, including bringing a tip face of an opticalfiber into contact with the adhesive agent, emitting light from the tipface of the optical fiber to the adhesive agent, detecting lightreturning from an interface between the tip face of the optical fiberand the adhesive agent to the optical fiber, and forming a new tip faceof the optical fiber after the degree of cure is measured.

The step of forming the tip face may include cutting the optical fiberand polishing a new tip face formed by cutting the optical fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a degree of cure measuring apparatusaccording to a first embodiment of the present invention;

FIG. 2 is a diagram illustrating the structure of a probe;

FIG. 3 is a diagram illustrating functional blocks of a computer;

FIG. 4 is a diagram showing examples of time-variation of refractiveindices;

FIG. 5 is a diagram showing another example of time-variation ofrefractive index;

FIG. 6 is a diagram illustrating a modification of the probe;

FIG. 7 is a diagram illustrating another modification of the probe;

FIGS. 8A and 8B are diagrams illustrating a refractive index measuringapparatus according to a second embodiment of the present invention;

FIG. 9 is a diagram illustrating a degree of cure measuring apparatusaccording to a third embodiment of the present invention;

FIG. 10 is a diagram illustrating the structure of a probe;

FIG. 11 is a diagram illustrating functional blocks of a computer;

FIG. 12 is a diagram showing examples of time-variation of refractiveindices;

FIG. 13 is a diagram illustrating another modification of the probe;

FIG. 14 is a diagram illustrating another modification of the probe;

FIG. 15 is a diagram illustrating another modification of the probe;

FIG. 16 is a diagram illustrating another modification of the probe;

FIGS. 17A and 17B are diagrams illustrating a degree of cure measuringmethod according to the third embodiment of the present invention; and

FIG. 18 is a diagram illustrating a degree of cure measuring methodaccording to a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by reference to the preferredembodiments. This does not intend to limit the scope of the presentinvention, but to exemplify the invention.

A degree of cure measuring apparatus for adhesive agent according to anembodiment of the present invention will be described.

First Embodiment

FIG. 1 is a diagram illustrating a degree of cure measuring apparatus 10according to a first embodiment of the present invention. As illustratedin FIG. 1, the degree of cure measuring apparatus 10 has a laser diode(LD: Laser Diode) 12, an LD driving circuit 14 for driving the laserdiode 12, an optical splitter 16, a probe 18, a detector 20, a firstoptical fiber 24 by which the laser diode 12 and the optical splitter 16are connected to each other, a second optical fiber 26 by which theoptical splitter 16 and the probe 18 are connected to each other, athird optical fiber 28 by which the optical splitter 16 and the detector20 are connected to each other, and a computer 22 connected to thedetector 20. The degree of cure measuring apparatus 10 is a apparatusfor measuring the degree of cure of adhesive agent 36 held in the probe18.

The laser diode 12 emits measurement light to be applied to the adhesiveagent 36, and a laser diode having an emission center wavelength of1,550 nm may be used as the laser diode 12, for example. The power ofthe measurement light emitted from the laser diode 12 is controlled bythe LD driving circuit 14.

The measurement light emitted from the laser diode 12 passes through thefirst optical fiber 24, and is input to the optical splitter 16. Asingle mode optical fiber is suitably used as the first optical fiber24.

The optical splitter 16 has a function of outputting light input fromthe first optical fiber 24 to the second optical fiber 26 and outputtinglight input from the second optical fiber 26 to the third optical fiber28. Accordingly, measurement light input from the laser diode 12 to theoptical splitter 16 through the first optical fiber 24 propagatesthrough the second optical fiber 26, and then is emitted from the probe18 provided to the tip of the second optical fiber 26. A single modeoptical fiber is suitably used as the second optical fiber 26 as in thecase of the first optical fiber 24.

FIG. 2 is a diagram illustrating the structure of the probe 18. Asillustrated in FIG. 2, the probe 18 has a capillary 30 provided to a tipportion of the second optical fiber 26, a cylindrical glass pipe 32 inwhich the capillary 30 is inserted, and a glass plate 34 provided to atip portion of the glass pipe 32.

The capillary 30 is a cylindrical member having a minute through holeformed at the center thereof, and the second optical fiber 26 isinserted in the through hole. A tip face of the capillary 30 and a tipface 26 a of the second optical fiber 26 are arranged within the sameplane so as to be vertical to the axis of the second optical fiber 26.The capillary 30 is inserted in the glass pipe 32 by about half of thewhole length of the glass pipe 32. A space 33 for holding the adhesiveagent 36 (referred to as “adhesive agent holding space”) is formed by aninner wall surface of the glass pipe 32, the tip face of the capillary30 and the tip face 26 a of the second optical fiber 26. The glass plate34 is provided so as to block an opening of the adhesive agent holdingspace 33, and the adhesive agent 36 is enclosed in the adhesive agentholding space 33.

In this embodiment, the adhesive agent 36 is filled in the adhesiveagent holding space 33. Accordingly, the tip face 26 a of the secondoptical fiber 26 and the adhesive agent 36 are brought into contact witheach other. Under this state, measurement light is applied from the tipface 26 a of the second optical fiber 26 to the adhesive agent 36. Themeasurement light is reflected from the interface between the adhesiveagent 36 and the tip face 26 a of the second optical fiber 26, and thenincident from the tip face 26 a into the core of the second opticalfiber 26. The reflection light returning from the interface between theadhesive agent 36 and the tip face 26 a to the second optical fiber 26is input to the optical splitter 16.

Here, in this embodiment, a surface of the glass plate 34 that faces thetip face 26 a of the second optical fiber 26 is tilted at apredetermined angle with respect to the tip face 26 a of the secondoptical fiber 26. This is because light passing through the adhesiveagent 36 and reflecting from the glass plate 34 is prevented fromreturning to the core of the second optical fiber 26.

Returning to FIG. 1, the reflection light input from the second opticalfiber 26 is output to the third optical fiber 28 by the optical splitter16. A single mode optical fiber is suitably used as the third opticalfiber 28 as in the case of the first optical fiber 24 and the secondoptical fiber 26.

The detector 20 detects the light amount of the reflection light inputfrom the third optical fiber 28, and outputs the detection result to thecomputer 22. A photodiode or the like is suitably used as the detector20.

FIG. 3 is a diagram illustrating functional blocks of the computer 22.As illustrated in FIG. 3, the computer 22 has a reflectance calculator40, a refractive index calculator 45 and a refractive index recorder 46.The respective blocks described in this specification are obtained in ahardware style (on a hardware basis) by elements such as a CPU of acomputer or mechanical devices or obtained in a software style (on asoftware basis) by computer programs and the like. In FIG. 3, functionalblocks obtained by the cooperation of these elements are illustrated.Accordingly, it is understandable by persons skilled in the art thatthese functional blocks can be obtained in various styles by thecombination of software and hardware elements.

The light amount of reflection light detected by the detector 20 isinput to the reflectance calculator 40. The emission light amount (thelight amount of measurement light) from the tip face 26 a of the secondoptical fiber 26 is also input to the reflectance calculator 40. Thisemission light amount may be calculated from driving current of thelaser diode 12. Furthermore, the emission light amount may be obtainedby measuring an emission light amount from the tip face 26 a in advancebefore the adhesive agent 36 is injected.

The reflectance calculator 40 calculates the rate of the detection lightamount I2 detected by the detector 20 to the emission light amount I1from the tip face 26 a of the second optical fiber 26, that is, thereflectance BR at the interface between the adhesive agent 36 and thetip face 26 a of the second optical fiber 26. A calculating formula forthe reflectance BR is represented by the following formula (1).

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack \mspace{619mu}} & \; \\{{BR} = {10\; \log_{10}\frac{I\; 2}{I\; 1}}} & (1)\end{matrix}$

The refractive index calculator 45 calculates the refractive index n ofthe adhesive agent 36 based on the reflectance BR calculated by thereflectance calculator 40. A calculating formula for the refractiveindex n of the adhesive agent 36 is represented by the following formula(2). The formula (2) can be derived by modifying Fresnel's reflectanceformula.

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack \mspace{619mu}} & \; \\{n = {{- \frac{1 + \sqrt{10^{\frac{BR}{10}}}}{1 - \sqrt{10^{\frac{BR}{10}}}}} \times n^{\prime}}} & (2)\end{matrix}$

In the formula (2), n′ represents the refractive index of the core ofthe second optical fiber 26.

The refractive index recorder 46 records the time-variation of therefractive index calculated by the refractive index calculator 45. Therefractive index recorder 46 may output the thus-recorded time-variationof the refractive index to a paper medium or display the recordedtime-variation on a display. The degree of cure of the adhesive agent 36can be grasped by obtaining the time-variation of the refractive index.

FIG. 4 shows examples of the time-variation of the refractive indices.Specifically, FIG. 4 shows the time-variation of the refractive indexobtained when Adhesive Epo-Tek® 353ND produced by Epoxy TechnologyCompany (hereinafter referred to as adhesive agent 1) is used as theadhesive agent. In FIG. 4, the vertical axis represents the refractiveindex, and the horizontal axis represents the time (minute) from thestart of curing of the adhesive agent. Standard curing conditions of theadhesive agent 1 are 80° C.-30 minutes, 100° C.-10 minutes, 120° C.-5minutes and 150° C.-1 minute.

After the adhesive agent 1 is enclosed in the adhesive agent holdingspace 33 of the probe 18 as illustrated in FIG. 2, the probe 18 is putinto a furnace whose temperature was raised to a predeterminedtemperature, and variation of the refractive index with time lapse ismeasured. In FIG. 4, a dashed line 41 represents the time-variation ofthe refractive index of the adhesive agent 1 at the furnacetemperature=80° C., a long dotted line 42 represents the time-variationof the refractive index of the adhesive agent 1 at the furnacetemperature=90° C., a dotted line 43 represents the time-variation ofthe refractive index of the adhesive agent 1 at the furnacetemperature=100° C., and a solid line 44 represents the time-variationof the refractive index of the adhesive agent 1 at the furnacetemperature=120° C. The first to third optical fibers are single modeoptical fibers, and the refractive index n′ of the cores thereof is setto 1.46.

In FIG. 4, each of the curved lines 41 to 44 varies where the refractiveindex thereof increases with time lapse after the refractive indextemporarily decreases, and then the refractive index becomes constantwhen some time elapses. The time period from the time at which curing ofthe adhesive agent 1 starts till the time at which the refractive indexbecomes constant is different among the curves. When the degree of cureof the adhesive agent 1 is measured at the time point when therefractive index becomes constant, the degree of cure reaches apredetermined degree of cure. Accordingly, the time period from thestart time of curing till the time at which the refractive index becomesconstant can be determined as a curing completion time for the adhesiveagent 1. The curing completion time obtained from FIG. 4 issubstantially coincident with the standard curing condition describedabove.

FIG. 5 shows another example of time-variation of the refractive index.Specifically, FIG. 5 shows the time-variation of the refractive indexobtained when Adhesive Epo-Tek® 301-2 produced by Epoxy TechnologyCompany (hereinafter referred to as adhesive agent 2) is used as theadhesive agent. The standard curing condition of the adhesive agent 2 is80° C.-3 hours.

As in the case of the adhesive agent 1, after the adhesive agent 2 isenclosed in the adhesive agent holding space 33 of the probe 18, theprobe 18 is put into a furnace whose temperature was raised to apredetermined temperature, and the variation of the refractive index ofthe adhesive agent 2 with time lapse is measured. In FIG. 5, a curvedline 51 represents a time-variation of the refractive index at thefurnace temperature of 80° C.

As shown in FIG. 5, the curved line 51 varies where after the refractiveindex temporarily decreases, the refractive index increases with timelapse and then becomes constant when about 65 minutes elapses from startof curing. When the degree of cure of the adhesive agent 2 is measuredat the time point when the refractive index becomes constant, the degreeof cure reaches a predetermined degree of cure. Accordingly, the timeperiod from the time when curing starts till the time when therefractive index becomes constant can be determined as a curingcompletion time for the adhesive agent 2.

As described above, according to the degree of cure measuring apparatus10 of this embodiment, the curing completion time of the adhesive agentcan be measured with high precision by measuring the time-variation ofthe refractive index of the adhesive agent. According to the degree ofcure measuring apparatus 10, the time-variation of the degree of cure ofthe adhesive agent can be measured, and information as to how long ittakes to cure the adhesive agent by about 50% of degree of cure can beobtained, for example.

As described above, a single mode optical fiber is preferably used asthe second optical fiber 26 used for the probe 18. Since the single modeoptical fiber has a small core diameter of 10 μm or less, light otherthan light reflected from the interface between the tip face 26 a of thesecond optical fiber 26 and the adhesive agent 36 (light which istemporarily incident into the adhesive agent 36 and then irregularlyreflected or the like) is hardly incident. Accordingly, the refractiveindex of the adhesive agent 36 can be stably measured.

In the above embodiment, the adhesive agent 36 is enclosed in theadhesive agent holding space 33 by using the glass plate 34. However,the tip face 26 a of the second optical fiber 26 and the adhesive agentcan be kept in contact with each other without providing the glass plate34 insofar as the probe 18 is set while the open face of the adhesiveagent holding space 33 faces the vertically upper side.

FIG. 6 illustrates a modification of the probe 18. In this modification,the tip portion of the second optical fiber 26 is provided with thecapillary 30. A recess portion 37 for holding the adhesive agent 36 isformed at the tip portion of the capillary 30. The tip face 26 a of thesecond optical fiber 26 is exposed to the internal space of the recessportion 37. For example, the bottom surface of the recess portion 37 andthe tip face 26 a of the second optical fiber 26 may be arranged on thesame plane.

When the adhesive agent 36 is injected into the recess portion 37 in thethus-formed probe 18, the tip face 26 a of the second optical fiber 26and the adhesive agent 36 come into contact with each other.Accordingly, as in the case of the probe described with reference toFIG. 2, light reflected from the interface between the tip face 26 a ofthe second optical fiber 26 and the adhesive agent 36 can be detected.

FIG. 7 illustrates another modification of the probe 18. The probe 18according to this modification is configured so that the capillary 30 isprovided to the tip portion of the second optical fiber 26. The tip faceof the capillary 30 and the tip face 26 a of the second optical fiber 26are arranged on the same plane.

The probe 18 of this modification is can be used to measure the degreeof cure of the adhesive agent 36 placed on the glass plate 39, forexample. In this modification, the probe 18 is disposed so that the tipface 26 a of the second optical fiber 26 comes into contact with theadhesive agent 36, whereby light reflected from the interface betweenthe tip face 26 a of the second optical fiber 26 and the adhesive agent36 can be detected.

In this modification, the glass plate 39 is preferably tilted at apredetermined angle with respect to the tip face 26 a of the secondoptical fiber 26. This is to prevent light reflected from the glassplate 39 from returning to the core of the second optical fiber 26.

Second Embodiment

FIGS. 8A and 8B are diagrams illustrating a refractive index measuringapparatus according to a second embodiment of the present invention. Therefractive index measuring apparatus according to this embodiment is aapparatus for measuring the absolute refractive index of a material.

The refractive index measuring apparatus according to this embodimenthas a similar structure to the degree of cure measuring apparatus 10illustrated in FIG. 1. In this embodiment, the probe 18 is configured sothat the capillary 30 is provided to the tip portion of the secondoptical fiber 26. The tip face of the capillary 30 and the tip face 26 aof the second optical fiber 26 are arranged on the same plane. A methodof measuring the absolute refractive index by using the refractive indexmeasuring apparatus according to this embodiment will be describedbelow.

First, as illustrated in FIG. 8A, the tip face 26 a of the secondoptical fiber 26 is brought into contact with a material M1 whoseabsolute refractive index is known, and the material M1 is irradiatedwith measurement light. The material M1 may be air (absolute refractiveindex=1) or water (absolute refractive index=1.33), for example.Reflection light reflecting from the interface between the material M1and the tip face 26 a and returning to the second optical fiber 26 isdetected by a detector (not shown).

When the absolute refractive index of the core of the second opticalfiber 26 is represented by nc, the absolute refractive index of thematerial M1 is represented by n1 and the light amount of measurementlight is represented by I0, the light amount I1 of the reflection lightis represented by the following formula (3) from the Fresnel'sreflectance formula.

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 3} \right\rbrack \mspace{619mu}} & \; \\{{I\; 1} = {\left( \frac{{nc} - {n\; 1}}{{nc} + {n\; 1}} \right)^{2} \times I\; 0}} & (3)\end{matrix}$

Accordingly, by measuring the light amount I1 of the reflection light,the light amount I0 of the measurement light can be obtained from thefollowing formula (4).

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 4} \right\rbrack \mspace{619mu}} & \; \\{{I\; 0} = \frac{I\; 1}{\left( \frac{{nc} - {n\; 1}}{{nc} + {n\; 1}} \right)^{2}}} & (4)\end{matrix}$

Subsequently, a material M2 whose absolute refractive index is unknownis irradiated with measurement light having the same light amount I0 asthat applied to the material M1. When the absolute refractive index ofthe material M2 is represented by n2 and the light amount of thereflection light is represented by I2, the following formula (5) issatisfied from the Fresnel's reflectance formula.

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 5} \right\rbrack \mspace{619mu}} & \; \\{{I\; 2} = {\left( \frac{{nc} - {n\; 2}}{{nc} + {n\; 2}} \right)^{2} \times I\; 0}} & (5)\end{matrix}$

Accordingly, by measuring the light amount I2 of the reflection lightreturning from the interface between the material M2 and the tip face 26a to the second optical fiber 26, the absolute refractive index n2 ofthe material M2 can be obtained from the formula (5).

In a case of adhesive agent containing much filler, light emitted fromthe optical fiber may irregularly reflected from the filler, and a partof the light may return to the optical fiber. In this case, the detectedlight amount is varied under uncured state; however, the variation isreduced as curing progresses. Accordingly, the degree of cure of theadhesive agent may be determined based on the fact that the variation inthe detected light amount is nullified.

Furthermore, in the first and second embodiments, the degree of cure ofthe adhesive agent is measured by obtaining the time-variation of therefractive index of the adhesive agent. However, the degree of cure ofthe adhesive agent can be measured by obtaining the time-variation oflight returning from the interface between the tip face of the opticalfiber and the adhesive agent to the optical fiber.

Third Embodiment

FIG. 9 is a diagram illustrating a degree of cure measuring apparatusaccording to a third embodiment of the present invention. As illustratedin FIG. 9, a degree of cure measuring apparatus 1010 has a laser diode(LD: Laser Diode) 1012, an LD driving circuit 1014 for driving the laserdiode 1012, an optical splitter 1016, a probe 1018, a detector 1020, afirst optical fiber 1024 by which the laser diode 1012 and the opticalsplitter 1016 are connected to each other, a second optical fiber 1026by which the optical splitter 1016 and the probe 1018 are connected toeach other, a third optical fiber 1028 by which the optical splitter1016 and the detector 1020 are connected to each other, and a computer1022 connected to the detector 1020. The degree of cure measuringapparatus 1010 is a apparatus for measuring the degree of cure ofadhesive agent 1036 placed on a glass plate 1039.

The laser diode 1012 emits measurement light to be applied to theadhesive agent 1036, and a laser diode having an emission centerwavelength of 1,550 nm may be used as the laser diode 1012, for example.The power of the measurement light emitted from the laser diode 1012 iscontrolled by the LD driving circuit 1014.

The measurement light emitted from the laser diode 1012 passes throughthe first optical fiber 1024 and is input to the optical splitter 1016.A single mode optical fiber is suitably used as the first optical fiber1024.

The optical splitter 1016 has a function of outputting light input fromthe first optical fiber 1024 to the second optical fiber 1026, andoutputting light input from the second optical fiber 1026 to the thirdoptical fiber 1028. Accordingly, measurement light input from the laserdiode 1012 to the optical splitter 1016 through the first optical fiber1024 propagates through the second optical fiber 1026, and then isemitted from the probe 1018 provided to the tip of the second opticalfiber 1026. A single mode optical fiber is suitably used as the secondoptical fiber 1026 as in the case of the first optical fiber 1024.

FIG. 10 is a diagram illustrating the structure of the probe. Asillustrated in FIG. 10, the probe 1018 has a capillary 1030 provided toa tip portion of the second optical fiber 1026, a light guide member1034 provided at a front side of the capillary 1030, and a split sleeve1031 for connecting the capillary 1030 and the light guide member 1034.

The capillary 1030 is a cylindrical member having a minute through holeformed at the center thereof, and the second optical fiber 1026 isinserted through the through hole. A tip face 1026 a of the secondoptical fiber 1026 is configured as a slope surface tilted with respectto the axis of the second optical fiber 1026 to prevent light reflectedfrom the joint point thereof with the light guide member 1034 fromreturning to the second optical fiber 1026. A tip face of the capillary1030 is configured as a slope face which is arranged on the same planeas the tip face 1026 a of the second optical fiber 1026.

The light guide member 1034 has an optical fiber piece 1032 and acapillary piece 1033. A single mode optical fiber is suitably used asthe optical fiber piece 1032. In this case, it is preferable that thesame optical fiber as the second optical fiber 1026 be used for theoptical fiber piece 1032 from the viewpoint of a connecting efficiency.The capillary piece 1033 is a cylindrical member having a minute throughhole formed at the center thereof, and the optical fiber piece 1032 isinserted through the through hole. A first end face 1032 a of theoptical fiber piece 1032 that is connected to the tip face 1026 a of thesecond optical fiber 1026 is configured as a slope surface in accordancewith the tip face 1026 a of the second optical fiber 1026. Furthermore,a first end face of the capillary piece 1033 that faces the tip face ofthe capillary 1030 is configured as a slope surface arranged on the sameplane as the first end face 1032 a of the optical fiber piece 1032. Asecond end face 1032 b of the optical fiber piece 1032 and a second endface of the capillary piece 1033 are formed on the same plane so as tobe vertical to the axis of the optical fiber piece 1032.

The capillary 1030 and the capillary piece 1033 are inserted in thesplit sleeve 1031. The optical fiber piece 1032 with the capillary 1030is detachably connected to the second optical fiber 1026 by the splitsleeve 1031. Under a joint state, the tip face 1026 a of the secondoptical fiber 1026 and the first end face 1032 a of the optical fiberpiece 1032 come into contact with each other, and measurement lightemitted from the tip face 1026 a of the second optical fiber 1026 isincident from the first end face 1032 a of the optical fiber piece 1032into the fiber, and emitted from the second end face 1032 b at theopposite side.

After the degree of cure of the adhesive agent 1036 is measured, theprobe 1018 is disposed so that the second end face 1032 b of the opticalfiber piece 1032 comes into contact with the adhesive agent 1036. Underthis state, measurement light is applied from the second end face 1032 bof the optical fiber piece 1032 to the adhesive agent 1036. Thismeasurement light is reflected from the interface between the adhesiveagent 1036 and the second end face 1032 b of the optical fiber piece1032, and then incident from the second end face 1032 b to the core ofthe optical fiber piece 1032 again. Reflection light returning from theinterface between the adhesive agent 1036 and the second end face 1032 bto the optical fiber piece 1032 is input to the optical splitter 1016through the second optical fiber 1026.

The glass plate 1039 on which the adhesive agent 1036 is placed ispreferably tilted at a predetermined angle with respect to the secondend face 1032 b of the optical fiber piece 1032. This is to preventlight passing through the adhesive agent 1036 and reflecting from theglass plate 1039 from returning to the optical fiber piece 1032.

Returning to FIG. 9, the optical splitter 1016 outputs the reflectionlight input from the second optical fiber 1026 to the third opticalfiber 1028. A single mode optical fiber is suitably used as the thirdoptical fiber 1028 as in the case of the first optical fiber 1024 andthe second optical fiber 1026.

The detector 1020 detects the light amount of reflection light inputfrom the third optical fiber 1028, and outputs the detected light amountto the computer 1022. A photodiode or the like is suitably used as thedetector 1020.

FIG. 11 is a diagram illustrating functional blocks of the computer. Asillustrated in FIG. 11, the computer 1022 has a reflectance calculator1040, a refractive index calculator 1045 and a refractive index recorder1046. The respective blocks described in this specification are obtainedin a hardware style (on a hardware basis) by elements such as a CPU of acomputer or mechanical devices or obtained in a software style (on asoftware basis) by computer programs and the like. In FIG. 11,functional blocks obtained by the cooperation of these elements areillustrated. Accordingly, it is understandable by persons skilled in theart that these functional blocks can be obtained in various styles bythe combination of software and hardware elements.

The light amount of reflection light detected by the detector 1020 isinput to the reflectance calculator 1040. The emission light amount (thelight amount of measurement light) from the second end face 1032 b ofthe optical fiber piece 1032 is input to the reflectance calculator1040. This emission light amount may be obtained based on the drivingcurrent of the laser diode 1012. Furthermore, the emission light amountfrom the second end face 1032 b may be measured in advance beforemeasurement.

The reflectance calculator 1040 calculates the rate of the detectedlight amount I2 detected by the detector 1020 to the emission lightamount I1 from the second end face 1032 b of the optical fiber piece1032, that is, the reflectance BR at the interface between the adhesiveagent 1036 and the tip face 1026 a of the second optical fiber 1026. Thecalculating formula for the reflectance BR is represented by thefollowing formula (6).

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 6} \right\rbrack \mspace{619mu}} & \; \\{{Br} = {10\; \log_{10}\frac{I\; 2}{I\; 1}}} & (6)\end{matrix}$

The refractive index calculator 1045 calculates the refractive index nof the adhesive agent 1036 based on the reflectance BR calculated by thereflectance calculator 1040. The calculating formula for the refractiveindex n of the adhesive agent 1036 is represented by the followingformula (7). The formula (7) can be derived by modifying the Fresnel'sreflectance formula.

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 7} \right\rbrack \mspace{619mu}} & \; \\{n = {{- \frac{1 + \sqrt{10^{\frac{BR}{10}}}}{1 - \sqrt{10^{\frac{BR}{10}}}}} \times n^{\prime}}} & (7)\end{matrix}$

In the formula (7), n′ represents the refractive index of the core ofthe second optical fiber 1026.

The refractive index recorder 1046 records the time-variation of therefractive index calculated by the refractive index calculator 1045. Therefractive index recorder 1046 may output the recorded time-variation ofthe refractive index to a paper medium or display the time-variation ona display. The degree of cure of the adhesive agent 1036 can be graspedby obtaining the time-variation of the refractive index.

FIG. 12 shows an example of the time-variation of the refractive index.Specifically, FIG. 12 shows the time-variation of the refractive indexobtained when Adhesive Epo-Tek® 353ND produced by Epoxy TechnologyCompany (hereinafter referred to as adhesive agent 1) is used as theadhesive agent. In FIG. 12, the vertical axis represents the refractiveindex, and the horizontal axis represents the time (minute) from startof curing. Standard curing conditions of the adhesive agent 1 are 80°C.-30 minutes, 100° C.-10 minutes, 120° C.-5 minutes and 150° C.-1minute.

As illustrated in FIG. 10, after the probe 1018 is disposed on theadhesive agent 1036, the probe 1018 and the adhesive agent 1036 are putinto a furnace whose temperature is increased to a predeterminedtemperature, and variation of the refractive index of the adhesive agent1036 with time lapse is measured. In FIG. 12, a dashed line 1041represents the time-variation of the refractive index at the furnacetemperature of 80° C., a long dotted line 1042 represents thetime-variation of the refractive index at the furnace temperature of 90°C., a dotted line 1043 represents the time-variation of the refractiveindex at the furnace temperature of 100° C., and a solid line 1044represents the time-variation of the refractive index at the furnacetemperature of 120° C. The first to third optical fibers and the opticalfiber pieces are single mode optical fibers, and the refractive index n′of the cores thereof is set to 1.46.

In FIG. 12, each of the lines 1041 to 1044 varies where, after therefractive index temporarily decreases, the refractive index increaseswith time lapse, and then becomes constant after some time elapses. Thetime period from the start time of curing till the time when therefractive index becomes constant is different among the curves. Whenthe degree of cure of the adhesive agent 1 is measured at the time pointwhen the refractive index becomes constant, the degree of cure reaches apredetermined degree of cure. Accordingly, the time period from thestart time of curing till the time when the refractive index becomesconstant can be determined as a curing completion time for the adhesiveagent 1. The curing completion time obtained from FIG. 12 issubstantially coincident with the standard curing conditions describedabove.

As described above, according to the degree of cure measuring apparatus1010 according to the third embodiment, the curing completion time forthe adhesive agent can be measured with high precision by measuring thetime-variation of the refractive index of the adhesive agent.Furthermore, according to the degree of cure measuring apparatus 1010,since the time-variation of the degree of cure of the adhesive agent canbe measured, information as to how long it takes to cure the adhesiveagent by about 50% of degree of cure can be obtained, for example.

The degree of cure measuring apparatus 1010 according to the thirdembodiment has the following advantages. When the degree of cure ismeasured while the tip face 1026 a of the second optical fiber 1026 isin direct contact with the adhesive agent 1036, the tip face 1026 a andthe adhesive agent 1036 adhere to each other by the curing of theadhesive agent 1036. Therefore, when the degree of cure of anotheradhesive agent is measured after the above measurement, it is necessaryto exchange the second optical fiber 1026 itself. However, according tothis embodiment, since the light guide member 1034 adhering to theadhesive agent 1036 can be detached from the probe 1018, only the lightguide member 1034 may be exchanged when the degree of cure of anotheradhesive agent is measured. Accordingly, according to the degree of curemeasuring apparatus 1010 of this embodiment, the degrees of cure ofplural kinds of adhesive agent can be inexpensively and easily measured.

As described above, a single mode optical fiber is preferably used asthe optical fiber piece 1032 used for the light guide member 1034. Sincethe core diameter of the single mode optical fiber is equal to 10 μm orless, which is small, light other than light reflected from theinterface between the second end face 1032 b of the optical fiber piece1032 and the adhesive agent 1036 (light which is temporarily incidentinto the adhesive agent 1036 and irregularly reflected and the like) ishardly incident into the core. Accordingly, the refractive index of theadhesive agent 1036 can be stably measured.

FIG. 13 illustrates a modification of the probe. A probe 1018 accordingto this modification is different from the probe illustrated in FIG. 10in that an adhesive agent holder 1038 for holding the adhesive agent1036 is further provided. The adhesive agent holder 1038 has acylindrical glass pipe 1035 inserted in the tip portion of the capillarypiece 1033, and a glass plate 1037 provided to a tip portion of theglass pipe 1035.

The capillary piece 1033 is inserted in the glass pipe 1035 till ahalfway position of the whole length of the glass pipe 1035. A space1047 for holding the adhesive agent 1036 (referred to as adhesive agentholding space) is formed by an inner wall surface of the glass pipe1035, the tip face of the capillary piece 1033 and the second end face1032 b of the optical fiber piece 1032. The glass plate 1037 is providedso as to block an opening of the adhesive agent holding space 1047,whereby the adhesive agent 1036 is enclosed in the adhesive agentholding space 1047.

In this modification, the adhesive agent 1036 is filled in the adhesiveagent holding space 1047. Accordingly, the second end face 1032 b of theoptical fiber piece 1032 and the adhesive agent 1036 come into contactwith each other. Under this state, the measurement light is applied fromthe second end face 1032 b of the optical fiber piece 1032 to theadhesive agent 1036. This measurement light returns from the interfacebetween the adhesive agent 1036 and the second end face 1032 b to theoptical fiber piece 1032, and is input to the optical splitter 1016through the second optical fiber 1026.

According to this modification, the measurement can be performed whilethe adhesive agent 1036 is held in the probe 1018; therefore, the probe1018 can be easily handled.

FIG. 14 illustrates another modification of the probe. A probe 1018illustrated in FIG. 14 is different from the probe illustrated in FIG.10 in that a lens 1050 as a light guide member for guiding measurementlight from the second optical fiber 1026 to the adhesive agent 1036 isprovided. The lens 1050 is disposed so that an incident face thereofcomes into contact with the tip face 1026 a of the second optical fiber1026. The incident face of the lens 1050 is configured as a slopesurface in accordance with the tip face of the capillary 1030 and thetip face 1026 a of the second optical fiber 1026.

The lens 1050 is configured so as to emit measurement light incidentfrom the tip face 1026 a of the second optical fiber 1026 as parallellight. The parallel light emitted from the lens 1050 returns from theinterface between the lens 1050 and the adhesive agent 1036 to the lens1050, and then is input to the detector 1020 through the second opticalfiber 1026.

Also in this modification, the lens 1050 adhering to the adhesive agent1036 can be detached from the probe 1018. Therefore, only the lens 1050may be exchanged when the degree of cure of another adhesive agent ismeasured. Accordingly, the degrees of cure of plural kinds of adhesiveagent can be measured inexpensively and easily.

FIG. 15 illustrates another modification of the probe. A probe 1018illustrated in FIG. 15 is different from the probe illustrated in FIG.10 in that a lens 1051 as a light guide member for guiding measurementlight from the second optical fiber 1026 to the adhesive agent 1036 isprovided. The lens 1051 is disposed so that an incident face thereofcomes into contact with the tip face 1026 a of the second optical fiber1026. The incident face of the lens 1051 is configured as a slopesurface in accordance with the tip face of the capillary 1030 and thetip face 1026 a of the second optical fiber 1026.

The lens 1051 is configured so that measurement light incident from thetip face 1026 a of the second optical fiber 1026 is focused onto a lightemission face. The measurement light emitted from the lens 1051 returnsfrom the interface between the lens 1051 and the adhesive agent 1036 tothe lens 1051, and then is input to the detector 1020 through the secondoptical fiber 1026.

Also in this modification, the lens 1051 adhering to the adhesive agent1036 can be detached from the probe 1018. Therefore, when the degree ofcure of another adhesive agent is measured, only the lens 1051 may beexchanged. Accordingly, the degrees of cure of plural kinds of adhesiveagent can be inexpensively and easily measured.

FIG. 16 illustrates another modification of the probe. A probe 1018illustrated in FIG. 16 is different from the probe illustrated in FIG.10 in that a lens 1052 and a light guide part 1054 as light guidemembers for guiding measurement light from the second optical fiber 1026to the adhesive agent 1036 are provided.

The lens 1052 is disposed so that an incident face thereof comes intocontact with the tip face 1026 a of the second optical fiber 1026. Thelens 1052 and the capillary 1030 are connected to each other by a splitsleeve 1031. The incident face of the lens 1052 is configured as a slopesurface in accordance with the tip face of the capillary 1030 and thetip face 1026 a of the second optical fiber 1026. The lens 1052collimates light incident from the tip face 1026 a of the second opticalfiber 1026. The lens 1052 is configured so that measurement lightincident from the tip face 1026 a of the second optical fiber 1026 isemitted as parallel light from a light emission face of the light guidepart 1054, as illustrated in FIG. 16.

The light guide part 1054 is disposed so that an incident face thereofcomes into contact with a light emission face of the lens 1052. Thelight guide part 1054 is configured in a rod-like shape, and detachablyconnected to the lens 1052 by the split sleeve 1053. In order to preventreflection, the connection face between the lens 1052 and the lightguide part 1054 is configured as a slope surface. The light guide part1054 is formed of a material having substantially the same refractiveindex as the adhesive agent 1036 before curing. When the degree of cureof the adhesive agent 1036 is measured, the light emission face of thelight guide part 1054 is brought into contact with the adhesive agent1036, and the adhesive agent 1036 is irradiated with light emitted fromthe lens 1052 under this state. Before the adhesive 1036 is cured, therefractive index of the light guide part 1054 and the refractive indexof the adhesive agent 1036 are substantially equal to each other, andtherefore there exits little reflection light returning from theinterface between the light guide part 1054 and the adhesive agent 1036to the second optical fiber 1026. However, when the adhesive agent 1036is cured and the refractive index thereof varies, reflection lightreturning from the interface between the light guide part 1054 and theadhesive agent 1036 to the second optical fiber 1026 occurs.Accordingly, the degree of cure of the adhesive agent 1036 can bedetected with high precision by detecting this reflection light.

In this modification, since the light guide part 1054 adhering to theadhesive agent 1036 can be detached from the probe 1018, only the lightguide part 1054 may be exchanged when the degree of cure of anotheradhesive agent is measured. Accordingly, the degrees of cure of pluralkinds of adhesive agent can be measured more inexpensively and easily.

FIGS. 17A and 17B are diagrams illustrating a degree of cure measuringmethod according to the third embodiment of the present invention. Inthis method, as illustrated in FIG. 17A, the tip face 1026 a of thesecond optical fiber 1026 is first brought into contact with theadhesive agent 1036, and measurement light is emitted from the tip face1026 a of the second optical fiber 1026 to the adhesive agent 1036 underthe above state. Thereafter, measurement light returning from theinterface between the tip face 1026 a of the second optical fiber 1026and the adhesive agent 1036 to the second optical fiber 1026 is detectedby using the detector 1020. After the degree of cure of the adhesiveagent 1036 is measured, the tip portion of the second optical fiber 1026adhering to the adhesive agent 1036 is cut by using a fiber cutter orthe like. Then, the newly formed tip face 1026 b of the second opticalfiber 1026 is polished for next measurement.

According to the degree of cure measuring method, the tip portion of thesecond optical fiber 1026 adhering to the adhesive agent is cut outafter the degree of cure is measured, whereby a new tip face formeasuring the degree of cure of another adhesive agent can be formed onthe second optical fiber 1026. According to this method, since anoptical element such as a light guide member is unnecessary, the degreeof cure of the adhesive agent can be measured more inexpensively.

Fourth Embodiment

FIG. 18 is a diagram illustrating a degree of cure measuring methodaccording to a fourth embodiment of the present invention. First, asecond optical fiber 1026 provided with a connector 1055 at an endportion thereof at the opposite side of the tip face 1026 a is used inthis method as illustrated in FIG. 18. The connector 1055 may bedirectly connected to the optical splitter 1016 or connected to a relayoptical fiber connected to the optical splitter 1016.

In this method, first, the tip face 1026 a of the second optical fiber1026 is brought into contact with the adhesive agent 1036, andmeasurement light is emitted from the tip face 1026 a of the secondoptical fiber 1026 to the adhesive agent 1036 under the above state asillustrated in FIG. 18. Thereafter, light returning from the interfacebetween the tip face 1026 a of the second optical fiber 1026 and theadhesive agent 1036 to the second optical fiber 1026 is detected byusing the detector 1020. After the degree of cure of the adhesive agent1036 is measured, the second optical fiber 1026 adhering to the adhesiveagent 1036 is detached from the optical splitter 1016. Then, anothersecond optical fiber is connected to the optical splitter 1016 for nextmeasurement.

According to the degree of cure measuring method, the degree of cure ofthe adhesive agent can be measured more easily than the method describedwith reference to FIG. 17 by exchanging the whole second optical fiber1026 adhering to the adhesive agent.

In the third and fourth embodiments described above, the degree of cureof the adhesive agent is measured by obtaining the time-variation of therefractive index. However, the degree of cure of the adhesive agent canbe measured by obtaining the time-variation of light returning from theinterface between the light guide member and the adhesive agent to theoptical fiber.

The embodiments of the present invention are described above. It isunderstandable by persons skilled in the art that these embodiments areexamples, various modifications may be made to the respectiveconstituent elements and the combination of the respective processingprocesses, and these modifications are within the scope of the presentinvention.

For example, the laser diode may be blinked at a frequency of about 100Hz to 10 kHz and only reflection light of these frequency components maybe detected. For example, the detector is provided with a lock-incircuit, and the reflection light is detected in synchronization withthe blinking of the laser diode 1012. In this case, the measurement canbe performed with higher sensitivity without being affected bydisturbance light.

Furthermore, a part of measurement light emitted from the laser diodemay be monitored to offset variation of a detected light amount causedby variation of the light amount of the measurement light. In this case,the refractive index can be measured with higher precision.

Still furthermore, in the above embodiments, the laser diode (LD) isused as a light source. However, a light emitting diode (LED: LightEmitting Diode) may be used as a light source.

In the above embodiments, the present invention is applied to the degreeof cure measuring apparatus for adhesive agent. However, the presentinvention is also applicable to measurement of the process of a reactioninvolving volume contraction.

1. A degree of cure measuring apparatus for measuring a degree of cureof adhesive agent, comprising: an optical fiber for emitting light froma tip face thereof; a probe for holding the adhesive agent and emittinglight to the adhesive agent while the adhesive agent is in contact withthe tip face of the optical fiber; and a detector for detecting lightreturning from an interface between the tip face of the optical fiberand the adhesive agent to the optical fiber.
 2. The degree of curemeasuring apparatus according to claim 1, further comprising arefractive index calculator for calculating a refractive index of theadhesive agent from a rate of a light amount detected by the detector toan emission light amount from the tip face of the optical fiber.
 3. Thedegree of cure measuring apparatus according to claim 2, furthercomprising a recorder for recording time-variation of the refractiveindex calculated by the refractive index calculator.
 4. The degree ofcure measuring apparatus according to claim 1, wherein the optical fiberis a single mode optical fiber.
 5. The degree of cure measuringapparatus according to claim 1, wherein the probe has a capillaryprovided to a tip portion of the optical fiber and a cylindrical memberin which the capillary is inserted, and an inner wall surface of thecylindrical member, a tip face of the capillary and the tip face of theoptical fiber form an adhesive agent holding space for holding theadhesive agent.
 6. The degree of cure measuring apparatus according toclaim 5, wherein the probe further has an enclosing member for enclosingthe adhesive agent in the adhesive agent holding space, a surface of theenclosing member that faces the tip face of the optical fiber beingtilted at a predetermined angle with respect to the tip face of theoptical fiber.
 7. The degree of cure measuring apparatus according toclaim 1, wherein the probe further has a capillary provided to a tipportion of the optical fiber, the capillary having a recess portion forholding the adhesive agent that is formed at a tip portion thereof.
 8. Adegree of cure measuring method for measuring a degree of cure ofadhesive agent, comprising: emitting light from a tip face of an opticalfiber; bringing the tip face of the optical fiber into contact with theadhesive agent; and detecting light returning from an interface betweenthe tip face of the optical fiber and the adhesive agent to the opticalfiber.
 9. The degree of cure measuring method according to claim 8,further comprising calculating a refractive index of the adhesive agentfrom a rate of a detected light amount to an emission light amount fromthe tip face of the optical fiber.
 10. The degree of cure measuringmethod according to claim 9, further comprising recording time-variationof the calculated refractive index.
 11. A degree of cure measuringapparatus for measuring a degree of cure of adhesive agent, comprising:an optical fiber for emitting light from a tip face thereof; a lightguide member detachably connected to the optical fiber and forirradiating the adhesive agent with light while a light emission facethereof is in contact with the adhesive agent; and a detector fordetecting light returning from an interface between the light emissionface of the light guide member and the adhesive agent to the light guidemember.
 12. The degree of cure measuring apparatus according to claim11, wherein the light guide member has an optical fiber piece connectedto the tip face of the optical fiber.
 13. The degree of cure measuringapparatus according to claim 11, wherein the light guide member has alens that is configured to emit light incident from the optical fiber asparallel light.
 14. The degree of cure measuring apparatus according toclaim 11, wherein the light guide member has a lens that is configuredso that light incident from the optical fiber is focused onto a lightemission face thereof.
 15. The degree of cure measuring apparatusaccording to claim 11, wherein the light guide member has a light guidepart for irradiating the adhesive agent with light incident theretowhile a light emission face thereof is in contact with the adhesiveagent, and that is formed of a material having substantially the samerefractive index as the adhesive agent before cure.
 16. The degree ofcure measuring apparatus according to claim 15, wherein the light guidemember further has a lens provided between the optical fiber and thelight guide part.
 17. The degree of cure measuring apparatus accordingto claim 11, further comprising a refractive index calculator forcalculating a refractive index of the adhesive agent from a rate of alight amount detected by the detector to an emission light amount fromthe light guide member.
 18. The degree of cure measuring apparatusaccording to claim 17, further comprising a recorder for recordingtime-variation of the refractive index calculated by the refractiveindex calculator.
 19. The degree of cure measuring apparatus accordingto claim 11, wherein the optical fiber is a single mode optical fiber.20. The degree of cure measuring apparatus according to claim 11,wherein the light guide member has an adhesive agent holder for holdingthe adhesive agent.
 21. A degree of cure measuring method for measuringa degree of cure of adhesive agent, comprising: bringing a tip face ofan optical fiber into contact with the adhesive agent; emitting lightfrom the tip face of the optical fiber to the adhesive agent; detectinglight returning from an interface between the tip face of the opticalfiber and the adhesive agent to the optical fiber; and forming a new tipface of the optical fiber after the degree of cure is measured.
 22. Thedegree of cure measuring method according to claim 21, wherein formingthe tip face includes: cutting the optical fiber; and polishing a newtip face formed by cutting the optical fiber.